Method of purifying lactalbumin



Jan. 10, 1950 w. E. TRUcE 2,494,148

METHOD 0F PURIFYING LACTALBUMIN Filed Jan. 22, 1947 ATTORNEY Patented Jan. 10, 1950 METHOD F PURIFYING LACTALBUMIN William E. Truce, La Fayette, Ind., assignor to Swift & Company, Chicago, Ill., a corporation of Illinois Application January 22, 194?, Serial No. 723,625

6 Claims.

The present invention relates to the treatmentv of lactalbumin, and more particularly to a method of purifying lactalbumin.

Lactalbumin, a heat-coagulable protein, is found in milk to the extent of about 0.5 per cent. Since lactalbumin is not precipitated with the casein in cheese-making, it remains as an important ingredient in whey, along with other substances, such as lactose, mineral constituents and traces of casein and fat.

Milk albumin, or lactalbumin, is recognized as a valuable protein. It contains the essential amino acids and, therefore, if taken in sucient amounts is capable of satisfying the protein requirements of the animal organism.

' Lactalbumin may be obtained from whey by the saturation thereof with certain salts followed by dilution, acidulation and, finally, long standing to effect crystallization. Another method of re covering lactalbumin from whey is to coagulate lactalbumin by means of heat. Lactalbumin may also be obtained from whey by precipitation with acid and heat. These methods of recovering lactalbumin from whey are inefficient and produc# tive of an inferior product, to the extent that heretofore whey has been utilized largely as an animal feed rather than a valuable source of.

lactalbumin.

A practical and eiiicient method of recovering lactalbumin from whey comprises the steps of.

neutralizing the whey to a point of total titratable acidity as lactic acid below 0.12 per cent, that is,

to a point below that at which the lactalbumin is coagulated when heated within the heat-coagulable temperature range thereof. This initial neutralization step is performed at a temperature below the heat-coagulable temperature range of lactalbumin, or under 155 F. Follow-k ing the neutralization step the whey is heated to methods such as the foregoing does not possess the degree of purity desired for pharmaceutical uses. For example, the lactalbumin clumps or curds prepared by the process herein disclosed, v

after being allowed to drain, are soft and gel-like and possess a solids content between about 15 and 2i) per cent of which only about 50 to 60 per cent is protein, the remainder being lactose and minerals contained in the liquid retained by the lactalbumin. This crude lactalbumin is not suitable for most pharmaceutical purposes, which require a protein content of about '70 per cent or above. Since some of the salts and lactose, or milk sugar, found in the crude lactalbumin are water soluble, it would seem expedient merely to` wash the crude lactalbumin to remove the watersoluble materials therefrom. It has been found, however, that because of the gelatinous nature of the crude lactalbumin, washing is often ineffective in raising the protein content thereof. The water retained by the lactalbumin and containing the lactose and minerals is so bound with the protein in a gel-like structure that repeated washings of the crude material do not increase the protein content the desired amount.

It is an object, therefor-e, of this invention to facilitate the purifying of lactalbumin and make possible the preperation of a superior lactalbumin product.

1n accordance with the invention, it is proposed to break the gel-like structure of the crude lactalbumin to free the moisture bound thereby, and thus permit washing of the protein.

It is contemplated by the invention to destroy the water holding properties of the crude lactalbumin by means of heat or heat and pressure under such controlled conditions that destruction of the gel structure of crude lactalbumin is effected without destroying the protein molecule.

Conditions of temperature and pressure are such as to cause destabilization of the protein and more particularly if the gel structure of the curd without degradation of the protein molecule, such as hydrolysis thereof.

In carrying out the invention, crude lactalbumin such as obtained in accordance with the process described herein, or any other diiicultly washed crude lactalbumin, is subjected to a heat treatment with or without pressure for a sufficient period of time to cause destabilization of the protein molecule and thereby permit Washing of the destabilized protein, as evidenced by the ready loss of water therefrom by draining a mixture thereof with water. By repeated washings of y the properly destabilized protein the lactose and some mineral constituents are removed from the crude lactalbumin and the protein content consequently increased. If desired, the washed lac-l talbumin may be dried, as hereinafter more fully described.

In one embodiment of the invention, destabilization of the protein molecule is effected, without hydrolyzing the same. by boiling the lactalbumin curds or clumps in an amount of water suicient to prevent scorching, or burning, of the protein, and for asuicient period of time, for example, about one-half hour. The destabilized protein is then washed by agitating with water and then the water allowed to drain therefrom.

Water freely leaves the destabilized protein mole.-

cule. By repeating the washings, additional amounts of lactose and mineralsv are removed;

from the crude lactalbuminv with a consequentrise in protein content. The foregoing procedure may result in protein yields representing about4 80 per cent or more of the solids content of the treated lactalbumin product.

It is understood that the amount of water in which the. crudelactalbumin is boiled may varywidely'.v Since the water serves to wash the destabiliaed protein the-upper. limits of the amounts' thereof are to be determined by the capacityof vthe equipment employed and the expense of. heating large quantities of material. The lower limitsoi water are suiiiciently high to prevent scorching, or burning, of the protein matter. A lower limit of about 1. volume of water for 1 volume. of crude lactalbumin has been foundv satisfactoryg, a suitable operating ratio being about 2 to 3 Volumes of water for l volume of-` crude lactalbumin.

The boiling time is preferably such as to cause destabilization of all of the protein matter and. not, for example, only of the surface thereof, thus leaving the interior unaffected. On thev other hand boiling should not be prolonged to the point that hydrolysis of theprotein molecule occurs, forv the, subsequent washing operations remove valuable fragments of protein material, thus detracting from the lvalue of the nal product. A boiling period oi about 30 minutes is suitable inlmost cases, although a period of 20 minutes, especially where boiling is vigorous and 40 minutes, where boiling approaches only simmer-ing intensity, have been found to be satisfactory.

In another embodiment of the invention, the gel structure of the crude lactalbumin may be destroyed with smaller volumes of water than are employed in the boiling process described above. The cru-de lactalbumin may be. autoclaved, i. e., subjected to the action of steam under pressure' in a closed' chamber or container. I have found' that the gel structure of the crude lactalbumin is broken in an autoclave in'about 15 minutes' at about l5 pounds steam pressure. It is understood that these conditions may vary overa widev range. Generally, the higher the pressure the less time required for the destruction ofthe gel', and the lowerthe pressure the more time required for the destabilization of the protein. It is` preferred not to employ pressures in excess ofA 15` pounds. For example, i0 to 30 minutesA at a pressure oi about 5 to l0 pounds, and 5 to 204 minutes at a pressure of about l5 pounds have' been found to b-e-suitable operating conditions in; autoclaying crude lactalbumin to effect the destabilization thereof without injury to the pro tein molecule.

Following the destabilisation` and washing op.. erations,y the resulting lactalbumin is in condition for drying; The destabilized, washedlactal buminmaybe spray-dried.roll-dried, or shelf:-

l ducted through line It to vessel I3.

4 dried. Before spray-drying, the mass of lactalburnin is broken up into small granular pieces and the proper fluidity for spray-drying effected. Suitable apparatus for subdividing the lactalbumin mass is, for example, a hammer mill. While the lactalbumin passes through the mill the proper uidity may be imparted to the resulting granules by the addition` of Water to cause a thinlactalbumin slurry or stream containing from about 5 to 15 per cent solids, a solids content of about 10 per cent being preferred in the. spray-drying operation. The lactalbumin dries to a powder containing a high proteirncontent;

The accompanying drawing illustrates diagrammatically a preferred embodiment of the invention.

In the drawing-the numeral I indicates a vat wherein the lactalbumin may be precipitated from the whey. The vatis provided with an outlet: 3; having; valve 4 throughwhichV excess liquid remainingv after; the,v formation` of lactalbumin.

may be drained. Precipitated"v lactalbumin may be charged through line 5,v provided with valve 1. to rotary iilter 9 provided with a filtrate discharge line; 8. In place of a rotary filter I may employ other means. for theexpulsion of moistureV fromthe crude: lactalbumin, such asa filter press ort acentrifuge. The crude lactalbumin is con- Vessel I3.l is preferably a, heat jacketed container, which may be employed for either boiling or autoclavv ingthecrude lactalbumin contained therein, and is. provided, with. gaugev i4 for recording pressures desired to be maintainedtherein. Following the destabilization.operation, the destabilized protein. is transferred through line I5 to Washing tanlell... Washing. tank Il'. is providedwith suitable agitating, means I3 whichmay be aiiixed to the. side. thereof and drivenby motor I9. The. tankY l1 may be provided with a waterY inlet and outlet,. not. shown, employed in washing the charged..lactalbumin` The washed lactalbumin is introduced'through line 2 l, provided with valve 22`, into. rotary lter'23 or other suitable means, such as a' centrifuge or filter press to separate wateixfromv the lactalbumin. The pressed lactalbumin is next charged to hammer mill 2l, or similar apparatus. for crushing or subdividing the protein. During the comminuting operation` inmill 2.1.,.water is introduced therein through 4line 26; whereby a slurry of desired dilution may be formed. The'. lactalbumin slurry leaves hammer mill'. 2T through line 28 and, by means of pump 29;.charged through line 3B, preheater 32 and1 lineA 34 tospray-drier 3B'. Drier 36 is providedv with a blower 3T' forv the introduction oft th'ebottom thereof' into bagY 43 or other suitablecontainer: Y

As-anll example-of' the'invention an amount of wheyf having a total titratable acidl content ofr about"0;2 per" cent was' neutralized ata tem-- perature oi" about 70?" Fi with. a mixture consisting of equal'- proportions of' sodium carbonate and sodium-` bicarbonate.

which aillpericent solution of'. hydrochloric acid was addeddown.the-sideV of thefvessel to bringt the. total titratableacidityof the'whey (as'lactic. acid) to: about. 0.25)l perf cent;

The neutralized whey-'1 was then heated to a temperature of 190 F., after' A lactalbumin.` curdiormedairthebottom of the-vessel, and was" scraped free therefrom. Lactalbumin curds also formed throughout the body of the whey and rose to the top, whence they were skimmed oli and allowed to drain. The lactalbumin mass having a solids content of about 17 per cent, with a protein proportion therein of about 62 per cent, was mixed with 2 volumes of water and the resulting mixture boiled for one-half hour. After the boiling operation the water drained freely from the lactalbumin. The lactalbumin was again mixed with 11/2 volumes of lukewarm water and the mixture agitated for about 5 minutes, after which the water was again drained olf. rIhe procedure of agitating and washing was repeated twice. IThe final protein proportion in the solids content was about 8l per cent. The protein product was then sent through a hammer mill, and while passing therethrough, sucient Water was added to bring the solids content of the resulting stream down to 10 per cent. This stream was then spray-dried into a white lactalbumin powder.

As a further illustrative example of the invention a quantity of lactalbumin product obtained in accordance with the procedure outlined in the foregoing example and having a solids content of about 20 per cent, of which 50 per cent was protein, was placed on a screen in an autoclave. Sufcient steam was introduced therein to effect a pressure of about pounds per square inch. After about 15 minutes the product was withdrawn and washed by agitating with 2 volumes of water and then draining. The spray-dried lactalbumin powder contained 82 per cent of protein.

Obviously, many modifications and Variations of the invention, as hereinbefore set forth, may

' be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a process of destabilizing gel-like aqueous curds of crude lactalbumin precipitated from whey without forming a solution of lactalbumin, the steps which comprise: heating in the presence of moisture the said curds of lactalbumin which have been separated from the whey to a temperature at least approximately the boiling point of water for a period of at least approximately 5 minutes while maintaining the lactalbumin in the solid state, and discontinuing the said heating before the said lactalbumin is hydrolyzed; thereby destabilizing the gel-like structure of the curds so that lactose and minerals normally associated with the crude -lactalbumin may be readily washed therefrom.

2. In a process of destabilizing gel-like aqueous curds of lactalbumin precipitated from whey without forming a solution of the lactalbumin, the step which comprises subjecting said aqueous curds of lactalbumin which have been separated from the whey to the action of steam under pressure while maintaining the lactalbumin in a solid state to destabilize the protein and discontinuing said action before the lactalbumin is hydrolyzed, whereby the destabilized product can be easily washed to remove the lactose and minerals normally associated therewith.

3. In a process of destabilizing gel-like aqueous curds of lactalbumin precipitated from whey without forming a solution of the lactalbumin, the step which comprises subjecting said aqueous curds of lactalbumin which have been separated from the whey to the action of steam under a pressure of about 5 to 15 pounds per square inch for about 5 to 30 minutes while maintaining the lactalbumin in a solid state to destabilize the protein, whereby the destabilized product can be easily washed to remove the lactose and minerals normally associated therewith.

li. In a process of purifying crude gel-like lactalbumin curds precipitated from whey without forming a solution of the lactalbumin, the step which comprises subjecting aqueous curds of lactalbumin which have been separated from the whey to the action of steam under a pressure of about i5 pounds per square inch for about 15 minutes while maintaining the lactalbumin in a solid state, thereafter agitating the treated lactalbumin with water and removing the water, whereby lactose and minerals arewasned from the lactalbumin.

5. In a process of purifying gel-like aqueous curds of crude lactalbumin obtained by precipitating from whey without forming a solution of the lactalbumin, the steps which comprise: admixing water with the gel-like curds of said lactalbumin which have been separated from the whey, heating the resulting mixture at a temperature approximately the boiling point of water for a period of between approximately 20 to 40 minutes while maintaining the lactalbumin in the solid state, and discontinuing said heating before the lactalbumin is hydrolized; thereby destabilizing the gel-like structure of the curds so that the lactose and minerals normally associated with the crude lactalbumin can be readily washed therefrom.

6. In a process of purifying the precipitated gel-like curds of crude lactalbumin obtained from whey without forming a solution of the lactalalbumin, the steps comprising: admixing at least approximately one volume of water with the gellike curds of said lactalbumin which have been separated from the whey, heating the said mixture at a temperature approximately the boiling point of water for approximately 30 minutes while maintaining the lactalbumin in the solid state, and discontinuing said heating before the said lactalbumin is hydrolized; thereby destabilizing the gel-like structure of the curds so that the lactose and minerals normally associated with the crude lactalbumin can be readily Washed therefrom.

WILLIAM E. TRUCE.

nnrnannons CITED- The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,023,014 Flanigan et al. Dec. 3, 1935 2,188,908 Lavett Feb. 6, 1940 2,377,853 Boyer g June 12, 1945 OTHER REFERENCES Utilisation of Whey, J. Royal Agriculture Society (England), vol. 83, pp. 73 to 96 (especially 77 and 78) (1922). 

1. IN A PROCESS OF DESTABILIZING GEL-LIKE AQUEOUS CURDS OF CRUDE LACTALBUMIN PRECIPITATED FROM WHEY WITHOUT FORMING A SOLUTION OF LACTALBUMIN, THE STEPS WHICH COMPRISE: HEATING IN THE PRESENCE OF MOISTURE THE SAID CURDS OF LACTALBUMIN WHICH HAVE BEEN SEPARATED FROM THE WHEY TO A TEMPERATURE AT LEAST APPROXIMATELY THE BOILING POINT OF WATER FOR A PERIOD OF AT LEAST APPROXIMATELY 5 MINUTES WHILE MAINTAINING THE LACTALBUMIN IN THE SOLID STATE, AND DISCONTINUING THE SAID HEATING BEFORE THE SAID LACTALBUMIN IS HYDROLYZED; THEREBY DESTABILIZING THE GEL-LIKE STRUCTURE OF THE CURDS SO THAT LACTOSE AND MINERALS 